The distribution of water through a municipality includes an extensive network of piping through which water is moved from storage and pumping stations to users. The piping includes numerous valves such that portions of the network can be closed off as needed for service while the remaining network remains operational. The pipes for a typical municipality will range from 3 inches in diameter to 36 inches in diameter, and the valves associated with such pipes have corresponding ranges and sizes.
The valves in the water systems of such a municipality may remain in the open condition or in the closed condition for long periods of time during which they are subjected to moisture and temperature changes, and the parts of the valves undergo certain deterioration over time. An infrequently operated valve often becomes frozen or locked into its position as a result of contamination and deterioration.
To open such valves, valve operating machines are provided which may be mounted on a truck or the like and positioned over the shaft leading to the valve. An elongate key has a lower end which fits around the stem of the valve, and the key is rotated by a hydraulic motor in the machine.
Existing truck mounted valve operating machines have a frame for mounting the machine to the bed of a truck. Positioned on the frame is a pair of spaced parallel tracks and slidable within the tracks is a table. Mounted on the table are a pair of hydraulic motors, and extending horizontally through the table is an polygon shaped aperture positioned between the motors through which a rotatable key having a complementarily shaped polygon cross section, can be fitted. To operate the valve turning machine a truck is positioned near a shaft leading to a valve. The table is slid along the tracks until it extends outward of the truck and over the shaft extending to the valve. Thereafter, a key is fitted through the aperture in the table and connected to the stem of the valve. The hydraulic motors are then operated to rotate the key and the valve stem to open or close the valve.
To receive an existing valve operating machines, a truck must be modified to accept the machine. If the machine is to be mounted on a pickup truck, the frame may be bolted to the bed of the truck and a hole cut in the side of the truck bed such that the table can extend outward through the hole. Alternatively, metal bars may be welded across the sides of the truck for mounting the machine in an elevated position over the bed to thereby avoid cutting a hole in the side of the truck. With this mounting, the table can slide across the top of the sides of the truck which border the bed. It would be desirable to provide a mounting for a valve operating machine which could be mounted on a truck without requiring that the truck be modified by the addition of mounting bars or cutting holes in the side of the truck.
Furthermore, operators have had difficulty inserting a key into the aperture extending through the table of existing machines. Existing machines provide a pair of hydraulic motors positioned in opposite sides of a bull gear having a central aperture which receives the key. The key itself is heavy, making it awkward to handle. Operators have found it difficult to insert the key through the aperture because the upper surface of the table is cluttered by the motors and other equipment mounted thereon.
Located within the bull gear in the table is a drive knuckle having a semispherical surface, and extending through the drive knuckle is the aperture having a polygon shaped cross-section into which the key is fitted. Movement of the knuckle enables the machine to receive a key which, because of the terrain on which the vehicle is positioned, or other factors, cannot be positioned perpendicular to the plane of the table. The knuckle includes a pivot ball fitted into a complementarily shaped socket. It is the pivot ball which has the vertical aperture extending therethrough for receiving the key. A pin extends from the inner wall of the socket and into a vertical groove in the side of the ball to transfer rotational movement from the socket in the bull gear to the ball of the drive knuckle in which the key is fitted. It has been found, however, that where the key is positioned several degrees from being perpendicular to the plane of the table, the ball in the knuckle will move back and forth with respect to the pin with each rotation of the bull gear and interfere with the smooth transfer of power to the drive key. It would be desirable, therefore, to provide a drive for transferring rotational motion from the bull gear to the drive key without the problems associated with the pins.
To operate a valve turning machine, the table must be locked with respect to the frame such that the table retains it orientation while the machine is in operation. Existing machines have a plurality of holes in one of the telescoping members on either the frame or the table and a corresponding hole in the other of the frame of the table, such that the holes in the two parts can be aligned and longitudinally locked by inserting a pin through the aligned holes. Typically, the locking holes are spaced a distance of approximately two inches apart along one of the members, so that the table can only be locked at intervals of two inches. It would be desirable to provide a table which can be locked at any location with respect to the frame such that the table can be more precisely positioned over a valve.